This invention relates generally to vasoocclusive devices, and more particularly concerns a mandrel for forming at least a portion of a vasoocclusive coil in a three dimensional configuration by winding of the coil about one or more portions of the mandrel.
Vasoocclusion devices are therapeutic devices that are placed within the vasculature of the human body, typically via a catheter, either to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus, or to form such an embolus within an aneurysm stemming from the vessel. The vasoocclusive devices can take a variety of configurations, and are generally formed of one or more elements that are larger in the deployed configuration than when they are within the delivery catheter prior to placement. One widely used vasoocclusive device is a helical wire coil having a deployed configuration which may be dimensioned to engage the walls of the vessels. For example, the vasoocclusive device may include one or more vasoocclusive members wound to form a generally spherical or ovoid shape in a relaxed state. Vasoocclusive members can be wound around an appropriately shaped mandrel or form and then heat-treated to retain the shape after removal from the heating form.
One type of mandrel used for winding and forming a vasoocclusive coil around the surface of the mandrel has a substantially spherical main body with six cylindrical posts having a diameter slightly smaller than that of the main body, disposed on the body and aligned with the three orthogonal x, y and z axes through the body of the mandrel, for aligning and shaping one or more portions of the vasoocclusive device as it is wound on the mandrel. One of the posts is longer than the other posts, to serve as a mandrel for helically winding a proximal portion of the vasoocclusive coil. In one variation of the mandrel, the mandrel has a main body that is substantially cubical, with six cylindrical posts disposed on each of the faces of the main body, and one of the posts being longer than the others.
Another type of mandrel has a substantially orthogonal main body with six cylindrical posts having a diameter slightly smaller than that of the main body, disposed on the body and aligned with the three orthogonal x, y and z axes through the body of the mandrel, for aligning and shaping the distal portion of the vasoocclusive device as it is wound on the mandrel. Preferably one of the posts is longer than the other posts, to serve as a mandrel for helically winding the proximal portion of the vasoocclusive coil. The mandrel may include a threaded aperture in a face of one of the posts and coaxially aligned with the orthogonal axis the post for receiving a corresponding end of a generally cylindrical handle, which is correspondingly threaded, and the handle can also be used as a mandrel for winding a portion of the vasoocclusive coil with a helical shape.
Another type of mandrel has a substantially spherical main body, with a plurality of circumferential grooves defined on the surface of the main body, and this type of mandrel may additionally have a plurality of posts mounted on the main body of the mandrel for aligning the occlusive device as it is wound on the mandrel. The surface of the mandrel may also have one or more apertures for receiving one or more ends of the strands, to assist winding into the desired form.
Heat treatment of the wound coil at a temperature of about 1100° F. for approximately four hours or more is typically sufficient to impart the form to the occlusive device when the shape memory material is a nickel titanium super-elastic alloy. After the heat treatment, the occlusive device is removed from the mandrel, and cold worked into the desired collapsed elongated configuration for placement into a catheter or cannula for use. When the occlusive device reaches its destination in the vasculature during vascular therapy, it assumes the primary shape imparted from the heat treatment on the mandrel.
Such spherical, cubical or orthogonal mandrels for winding of vasoocclusive coils have proved suitable for winding coils in such shapes, and allow for the combination of multiple coils or the winding of various shapes in an individual coil, but it would be desirable to provide a winding mandrel offering a greater variety of options for winding patterns for forming other shapes of vasoocclusive coils, such as for forming longer framing coils, and for providing shorter transitions between coils for coils with more than six loops, for example. The present invention satisfies these and other needs.